This invention relates to ink jet printer pens, and more particularly to monolithic or solid state print heads.
Ink jet printing mechanisms use pens that shoot droplets of colorant onto a printable surface to generate an image. Such mechanisms may be used in a wide variety of applications, including computer printers, plotters, copiers, and facsimile machines. For convenience, the concepts of the invention are discussed in the context of a printer. An ink jet printer typically includes a print head having a multitude of independently addressable firing units. Each firing unit includes an ink chamber connected to a common ink source, and to an ink outlet nozzle. A transducer within the chamber provides the impetus for expelling ink droplets through the nozzles.
To obtain high resolution printed output, it is desirable to maximize the density of the firing units, requiring miniaturization of print head components. When resolutions are sufficiently high, conventional manufacturing by assembling separately produced components becomes prohibitive. The substrate that supports firing resistors, the barrier that serves as a gasket to isolate individual resistors, and the orifice plate that provides a nozzle above each resistor are all subject to small dimensional variations that can accumulate to limit miniaturization. In addition, the assembly of such components for conventional print heads requires precision that limits manufacturing efficiency.
Monolithic print heads have been developed to provide a print head manufacturing process that uses photo imaging techniques similar to those used in semiconductor manufacturing. The components are constructed on a flat wafer by selectively adding and subtracting layers of various materials. Using photo-imaging techniques, dimensional variations are limited. Variations do not accumulate because each layer is registered to an original reference on the wafer. Existing monolithic print heads are manufactured by printing a mandrel layer of sacrificial material where firing chambers and ink conduits are desired, covering the mandrel with a shell material, then etching or dissolving the mandrel to provide a chamber defined by the shell. In the prior art, numerous firing chambers are interconnected as a single chamber, so that all may be fed by a single ink via drilled through the wafer into the chamber.
Existing monolithic print heads are complex to manufacture, and the interconnected nature of the ink chambers reduces the efficiency of ink expulsion. These disadvantages are overcome or reduced by providing an ink jet print head having a substrate with an upper surface, and an ink supply conduit passing through the substrate. An array of independently addressable ink energizing elements is attached to the upper surface of the substrate. An orifice layer has a lower surface conformally connected to the upper surface of the substrate, and has an exterior surface facing away from the substrate. The orifice layer defines a plurality of firing chambers, each passing through a respective nozzle aperture in the exterior surface, and extending downward through the orifice layer to expose a respective ink energizing element. Each of the firing chambers is separated from all other firing chambers by a portion of the orifice layer.